In the electronic industry, it is a goal to make a product smaller, thinner, lighter and cheaper. For an oscillator device such as a voltage-control oscillator, an inductor included therein is one of the potential elements for being altered so as to reduce the overall size of the oscillator. In conventional oscillators, an SMD inductor having a small size is used. As known to those skilled in the art, unfortunately, SMD inductors are of very high cost. Alternatively, an inductor formed in a microstrip line manner is provided at a lower cost. The inductor, however, needs too large surface and occupies too much space.